It is known to react water and an olefin in the presence of an acid catalyst and to employ a synthetic organic cation exchange resin in the acid form as that catalyst. Early patent references suggest that the water be maintained in the liquid phase. Specifically, U.S. Pat. No. 2,477,380 teaches that, while the water must be maintained in the liquid phase, it makes no difference whether the olefin is in the liquid or vapor phase. Another which teaches the necessity of maintaining the water of reaction at least partly in the liquid phase is U.S. Pat. No. 2,813,908.
More recently it has been taught that it is useful to employ a solvent which has solvency for both reactants--the water and the olefin. The solvent enhances the rate of hydration of forming solutions with the olefin and with the water, in each of which the product alcohol is soluble. This prevents the accumulation of the product alcohol at the catalyst surface and allows the reaction to approach equilibrium.
Solvents suggested for the purpose are oxygen-containing compounds, for example alcohols, ethers and ketones. Isopropyl alcohol, ethyl ether and acetone, among others, are specifically mentioned in U.S. Pat. No. 3,257,469. Separate phases of product alcohol-water-solvent and product alcohol-olefin-solvent are taught to be necessary in U.S. Pat. No. 3,285,977. Each of these phases is homogeneous, but immiscible with the other.
The present invention employs a single, homogeneous phase of olefin, water and solvent as the feed to the first stage of a three-stage reactor system and maintains the homogeneity throughout the course of the reaction. A further aspect of the invention is to feed less than all of the olefin to the first stage reactor and to feed the remainder into the second stage reactor, thereby decreasing the amount of solvent required. The product alcohol acts as a cosolvent together with the solvent added with the feed.